MC1R comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
In 2022, the INCB said, regarding state legalization, “The Board has repeatedly expressed its concern that these developments may be inconsistent with the country’s legal obligations as a party to the three international drug conventions." Since then, over 20 other US states have legalized non-medical cannabis use. In 2013, Uruguay legalized cannabis, with the law taking effect in April 2014, making it the first country to do so. The INCB condemned the move and stated that Uruguay "knowingly decided to break the universally agreed and internationally endorsed legal provisions". The statement continued: "Cannabis is not only addictive but may also affect some fundamental brain functions, IQ potential, and academic and job performance and impair driving skills. Smoking cannabis is more carcinogenic than smoking tobacco." In 2018, Canada legalized cannabis, with the law taking effect that October. In "A Framework for the Legalization and Regulation of Cannabis in Canada", it was acknowledged that "Canada is one of more than 185 Parties to three United Nations drug control conventions" and said: "...
== Biosynthesis == CDPS-encoding genes are found in genomic locations with genes encoding additional biosynthetic enzymes (CDPS DmtB1 is an example, encoded by the gene of dmt1 locus). These additional biosynthetic enzymes are for example: oxidoreductases, prenyltransferases, methyltransferases, or cyclases and some proteins as cytochrome P450s.
Meprobamate, 2-methyl-2-propyl-1,3-propanediol dicarbamate is synthesized by the reaction of 2-methylvaleraldehyde with two molecules of formaldehyde and the subsequent transformation of the resulting 2-methyl-2-propylpropan-1,3-diol into the dicarbamate via successive reactions with phosgene and ammonia.
== Adverse effects == People have had severe infusion-related reactions to pembrolizumab. There have also been severe immune-related adverse effects including lung inflammation (including fatal cases) and inflammation of endocrine organs that caused inflammation of the pituitary gland, of the thyroid (causing both hypothyroidism and hyperthyroidism in different people), and pancreatitis that caused Type 1 diabetes and diabetic ketoacidosis; some people have had to go on lifelong hormone therapy as a result (e.g. insulin therapy or thyroid hormones). People have also had colon inflammation, liver inflammation, kidney inflammation due to the drug. The common adverse reactions have been fatigue (24%), rash (19%), itchiness (pruritus) (17%), diarrhea (12%), nausea (11%) and joint pain (arthralgia) (10%). Other adverse effects occurring in between 1% and 10% of people taking pembrolizumab have included anemia, decreased appetite, headache, dizziness, distortion of the sense of taste, dry eye, high blood pressure, abdominal pain, constipation, dry mouth, severe skin reactions, vitiligo, various kinds of acne, dry skin, eczema, muscle pain, pain in a limb, arthritis, weakness, edema, fever, chills, myasthenia gravis, and flu-like symptoms.
== See also == Artificial intelligence in Brazilian industry Artificial intelligence industry in India Artificial intelligence industry in Italy Artificial intelligence industry in Taiwan Artificial intelligence industry in Canada Parliamentary Under-Secretary of State for AI and Digital Government Science and technology in the United Kingdom
Sources: en.wikipedia.org
=== Misdiagnosis === There is an ELISA-based test for brown recluse venom that can determine whether a wound is a brown recluse bite, although it is not commercially available and not in routine clinical use. Clinical diagnoses often use Occam's razor principle in diagnosing bites based on what spiders the patient likely encountered and previous similar diagnoses. Stoecker, Vetter & Dyer (2017) suggested the mnemonic "NOT RECLUSE", shown below, as a memory device to help laymen and medical professionals more objectively screen and diagnose potential cases of loxoscelism.
=== Sites of synthesis === Traditionally, RBP is synthesized within the liver with secretion being dependent upon retinol concentrations. However, the concentrations levels do not appear to have an effect upon transcription of RBP messenger RNA (mRNA) which remains constant. Literature reveals that the bovine endometrium has also been identified as a location of RBP synthesis, as well as, the conceptus and extraembryonic tissues of various livestock species.
A defining strength of the T32 program is its structured approach to career development. Each trainee develops an individualized training plan with guidance from a primary mentor and multidisciplinary mentoring committee. The program combines intensive laboratory research with didactic coursework, journal clubs, works-in-progress seminars, grant-writing workshops, responsible conduct of research training, scientific communication, peer-review experience, and individualized career development planning. Regular evaluations ensure that trainees achieve progressive scientific independence while developing the professional skills necessary to compete successfully for fellowships, career development awards, and independent research funding. The training environment emphasizes collaboration across basic, translational, and clinical research disciplines. Through participation in institute-wide seminars, center activities, collaborative research projects, and national scientific meetings, trainees interact with internationally recognized investigators and gain exposure to diverse scientific perspectives and emerging technologies. Access to state-of-the-art core facilities—including genomics, proteomics, metabolomics, imaging, pathology, bioinformatics, and animal model resources—provides trainees with advanced technical expertise while promoting interdisciplinary approaches to complex problems in aging research. The Barshop Institute's T32 program is distinguished by its long-standing record of success in preparing independent investigators.
== Specificity == Algicidal activity can be highly strain-specific and sometimes appears random or unexplained. Current studies have found that particle-associated bacteria tend to have broader algicidal activity, while free-living bacteria are often more species-specific. Algicidal bacteria with low host specificity may occupy a broader ecological niche as they can interact with and utilize organic matter from multiple algal species. However, highly specific bacteria may be more efficient in targeting particular algal hosts. Specificity does not necessarily determine bacterial abundance, but rather reflects different ecological strategies such as generalist versus specialist lifestyles.
Sources: en.wikipedia.org
"Ligament" most commonly refers to a band of dense regular connective tissue bundles made of collagenous fibers, with bundles protected by dense irregular connective tissue sheaths. Ligaments connect bones to other bones to form joints, while tendons connect bone to muscle. Some ligaments limit the mobility of articulations or prevent certain movements altogether. Capsular ligaments are part of the articular capsule that surrounds synovial joints. They act as mechanical reinforcements. Extra-capsular ligaments join in harmony with the other ligaments and provide joint stability. Intra-capsular ligaments, which are much less common, also provide stability but permit a far larger range of motion. Cruciate ligaments are paired ligaments in the form of a cross. Ligaments are viscoelastic. They gradually strain when under tension and return to their original shape when the tension is removed. However, they cannot retain their original shape when extended past a certain point or for a prolonged period of time. This is one reason why dislocated joints must be set as quickly as possible: if the ligaments lengthen too much, then the joint will be weakened, becoming prone to future dislocations. Athletes, gymnasts, dancers, and martial artists perform stretching exercises to lengthen their ligaments, making their joints more supple. The term hypermobility refers to the characteristic of people with more-elastic ligaments, allowing their joints to stretch and contort further; this is sometimes still called double-jointedness.
Activation of the coagulation system may precipitate disseminated intravascular coagulation. High potassium levels may lead to potentially fatal disruptions in heart rhythm. Phosphate binds to calcium from the circulation, leading to low calcium levels in the blood. Rhabdomyolysis may cause kidney failure by several mechanisms. The most important is the accumulation of myoglobin in the kidney tubules. Normally, the blood protein haptoglobin binds circulating myoglobin and other heme-containing substances, but in rhabdomyolysis the quantity of myoglobin exceeds the binding capacity of haptoglobin. Myoglobinuria, the presence of myoglobin in the urine, occurs when the level in plasma exceeds 0.5–1.5 mg/dL; once plasma levels reach 100 mg/dL, the concentration in the urine becomes sufficient for it to be visibly discolored and corresponds with the destruction of about 200 grams of muscle. As the kidneys reabsorb more water from the filtrate, myoglobin interacts with Tamm–Horsfall protein in the nephron to form casts (solid aggregates) that obstruct the normal flow of fluid; the condition is worsened further by high levels of uric acid and acidification of the filtrate, which increase cast formation. Iron released from the heme generates reactive oxygen species, damaging the kidney cells.
A tetramer stain is a flow cytometry procedure that uses tetrameric proteins to detect and quantify T cells that are specific for a given antigen within a sample (e.g. blood, CSF). The tetramers used in the assay are made up of four major histocompatibility complex (MHC) molecules, which are found on the surface of most cells in the body. Cells produce MHC molecules containing peptides as a way to display the products those cells are making. One important function of MHC presentation is to communicate the presence of viruses, bacteria, cancerous mutations, or other antigens in a cell. If a T cell receptor recognises the peptide being presented by an MHC molecule, expansion of that T cell occurs. MHC tetramers are bioengineered to present a specific peptide that can be used to identify T cells with receptors that match that peptide. Tetramers are labeled with a fluorophore, allowing tetramer-bound T cells to be analyzed with flow cytometry. Quantification and sorting of T-cells by flow cytometry enables researchers to investigate immune response to e.g viral infection and vaccine administration as well as functionality of antigen-specific T cells. Generally, if a person's immune system has encountered a pathogen, the individual will possess T cells with specificity toward some peptide on that pathogen. If a tetramer stain specific for a pathogenic peptide (e.g. the Influenza virus A nucleoprotein (NP)) is positive, this indicates expansion of influenza A virus specific T cells in the subject.
The epidermis contains no blood vessels, and cells in the deepest layers are nourished almost exclusively by diffused oxygen from the surrounding air and to a far lesser degree by blood capillaries extending to the outer layers of the dermis. The main type of cells that make up the epidermis are Merkel cells, keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strata (beginning with the outermost layer): corneum, lucidum (only in palms of hands and bottoms of feet), granulosum, spinosum, and basale. Cells are formed through mitosis at the basale layer. The daughter cells (see cell division) move up the strata changing shape and composition as they die due to isolation from their blood source. The cytoplasm is released and the protein keratin is inserted. They eventually reach the corneum and slough off (desquamation). This process is called "keratinization". This keratinized layer of skin is responsible for keeping water in the body and keeping other harmful chemicals and pathogens out, making skin a natural barrier to infection.
== Pathophysiology == LECT2 as a hepatokine, a substance made and released into the circulation by liver hepatocyte cells that acts as a hormone or signaling agent to regulate the function of other cells. While the pathogenesis of LECT2 amyloidosis is unclear, the intact LECT2 protein may have a tendency to fold abnormally thereby forming non-soluble fibrils that are deposited in tissues. It has been suggested that individuals with the disease have an increase in LECT2 production and/or a decrease in LECT2 catabolism (i.e. breakdown) which may increase its tendency to deposit in tissues. On the other hand, there are genetic variations which appear to cause the deposition of LECT2 in tissues. Studies to date have failed to obtain evidence for LECT2 gene mutations in the disorder but most cases examined in the United States are associated with a particular homozygous single nucleotide polymorphism (i.e. SNP) in the LECT2 gene. This SNP occurs in exon 3 at codon 58 of the gene, contains a guanine rather than adenine nucleotide at this site, and consequently codes for the amino acid valine rather than isoleucine. Although not yet proven to occur in vivo, the Val58Ile variant of LECT2 may have a propensity to fold abnormally, form insoluble fibrils, and therefore deposits in tissues. The Val58Ile LECT2 variant is common in Hispanics and appears to be the cause of their high incidence of LECT2 amyloidosis. However, not all homozygous Hispanic carriers of the variant ever exhibit LECT2 amyloidosis.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
It is a synthetic seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.